In the development of novel medicines lately, great importance has been attached to creating as high uptake as possible of the active ingredient. Common to all medicines which are not administered by an injection is that they have to penetrate a biological membrane, e.g. the skin or the intestinal wall.
In the medical field the development of formulations for local or dermal applications has for many years primarily aimed at changing the properties of the skin so as to accomplish a more rapid penetration thereof. Research in the TDDS field, i.e. transdermal delivery systems, has led to the discovery of several so called enhancers. Such substances are utilized to change the properties of the skin so as to facilitate the penetration of the drug therein. However, skin properties are not the only parameters that dictate how rapidly the body will assimilate a locally administered drug. Several other factors are of a great importance, such as for instance the contact between skin and formulation, the extent to which local circulation is effected by the formulation and the solubility of the drug in the formulation. The problems are similar whether the preparations are administered locally or systemically.
Specific problems are encountered in connection with drug substances which are poorly soluble in conventional aqueous and fatty carriers. Thus, the bioavailability of a drug of this type is dictated by its dissolution rate which, in turn, is dependent on substances's particle size and specific surface area, or polymorph condition. Thus, it has been proposed to solve the problem associated with such drugs by reducing their particle size as much as possible. Other more or less complicated methods to be mentioned in this context are lyophilization, solvent deposition, solvate formation and the use of so called solid dispersions.
The technique of using solid dispersion is for instance disclosed in WO93/11749. The process disclosed therein, however, does not provide a satisfactory solution to the problems associated with poorly water and fat soluble drugs, and it does not enable any substantial variation of the dissolution or release rates of an active agent. The major reason for this drawback is that the active ingredient is still not in any substantially dissolved state. Furthermore, although a plasticizer is referred to therein, it is clearly disclosed that said plasticizer is used to facilitate the formation of a dispersion, the product manufactured being a solid powdery mass.
As prior art in connection with the invention reference can also be made to U.S. Pat. No. 4,151,273 and U.S. Pat. No. 4,938,964. U.S. Pat. No. 4,151,273 discloses the use of a glassy matrix as a carrier for a drug but said carrier is more or less non-variably solid and used in a powdered product, e.g. a tablet, for oral administration. Moreover, it does not suggest the use of any plasticizer. U.S. Pat. No. 4,938,964 discloses an adhesive carrier for ketoprofen, comprising a specific acrylic or methacrylic copolymer. Thus, also said carrier has a more or less fixed composition that does not enable any real compositional adjustments after the preparation thereof and is laminated on a solid film support. Furthermore, again, U.S. Pat. No. 4,938,964 does not include any reference to a plasticizer.